Fluid pressure brake



July 21, 1936.

J. Nn GOOD FLUID PRESSURE BRAKE Filed Jan. 30, 1935 D W. w o M E O 0 V G T w. T N A N l w n w, wv WM lmN WW NWNW m.\\\k0\ MM, .mlm M WwN m6, uw. N Mm w .wm QW Nm. AQLQW m wm 5 Q m um 50 emergency Patented July 2l, 1936 FLUID PRESSURE BRAKE John N. Good,`Wilmerding, Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporationhof Pennsylvania Application January 30, 14935, Seriall No. 4,033 12 claims. (ciao3-46) This invention relates to iluid pressure brakes in which the brakes are applied and released by varying the iluid pressure in the brake pipe.

It has heretofore been proposedto provide brake equipment of the above type in which in effecting an emergency application of the brakes iiuid under pressure is initially supplied to the brake cylinder at a rate sufiicient to insure the movement of the brake cylinder piston so as to l0 cause the brake shoes to engage the wheels, after which iiuid is supplied tothe brake cylinder at a slow rate for a period of time `suiiicient to insure that the brakes Vwill .be applied on allof the cars of the train beforelthe brakes have been 15 appliedon the cars at the head end of the train with such force in advance of applying the brakes on the cars at the rear end of the train as to result in the running in of the slack in the train at such a rate that excessive shockswill be produced. After the brake cylinderbuild up delay period and after the slack has run in, the brake cylinder pressure is then permitted to build up at a rapid rate.

A fiuid pressure brake equipment having the above feature byV which in an emergency application there is an initial inshot of s fluid under pressure to the brake cylinder followed by aslow build up of brake cylinder' pressure, and thereafter followed by a final inshot of fluid under pressure to the brake cylinder isdisclosed in U. S. Patent No. 2,013,231, issued February '18, 1936 to Clyde C. Farmer. f

In the brake equipment shown ln the above identified application a restriction in the rate of 5 flo-w to the brake cylinder is produced by valve. means which is subject to the pressure of fluid supplied to the brake cylinder, and which during a service application of the brakes is rendered inoperative by the application of iluid under pres- L20 sure to both sides of theabutment which controls the operation of the valvemeans.`

In an emergency application of the brakes the movable abutment operates to close the valve when the brake cylinder pressure on one side of the abutment has been increased to a degree sufficient to overcome the pressure of a spring acting on the opposite side of the abutment. Normally the spring side ofthe abutment is connected to the atmosphere,` and Yon effecting an application the communication through which the spring sideA of the abutment is vented to the atmosphere is cut o, and possible leakage of fluid under pressure to the spring side of the abutment may then. interfere with the desired operation of the inshot valve meansy One object of my invention is to provide means for insuring that the desired operation of the inshot valve means will not be interfered with by possible leakage to the spring side of the operating abutment associated with .the inshot 5 valve means.

A further object of my invention is to provide a brake controlling valve device having a three stage build up of brake cylinder pressure in emergency feature with one stage controlled by valve l0 means operable subject to the pressure of fluid supplied to the brake cylinder and having means` to insure that theY operation of this valve means will not be aiected by leakage of fluid around the elements associated with the valve means or 15' with other portions of the brake controlling valve device. Y

Other objects of the invention and features of novelty will be apparent from the following de-4 scription taken in connection with the accom- 20. panying drawing which is a diagrammatic view of a fluid pressure brake equipment for a car including a brake controlling valve device shown in section and embodying my invention.

The equipment shown inthe drawing is similar 25 to that shown in the patent hereinbefore referred to, but only so much of the equipment is illustrated as is deemed necessary to a clear understanding of the present invention.

As shown in the drawing the equipment may 30 comprise a pipe bracket I to `which is secured a `triple valve casing 2 and an emergency valve casing 3. The brake pipe 4 is connected to a passage 5 in the pipe bracket I, a brake lcylinder 6 is connected by a pipe 1 to a passage 8 in the 35 pipe bracket I, an auxiliary reservoir 9 is connected by a pipe I0 to a passage II,` and the emergency reservoir I2 is connected by a pipe I3 to a passage Min the pipe bracket. f The triple valve casing 2 has a piston chamber 40 I5 connected to the brake pipe passage 5 and containing a piston I6, and'on the opposite side of the piston is a valve chamber I1 connected to the,` auxiliary reservoirpassage II and containing a main slide valve I8 and an auxiliary slide 45 valve I9 adapted to be operated by the piston I6 through the piston stem 20.

The emergency valve casing 3 contains an emergency valve device indicated generally at 2 I,

f to operate a valve 42 contained in the Valve cham thereof connected to the brake pipe passage 5 and on the opposite side of the piston is a valve chamber 28, connected through passage 29 with a quick action chamber 30, and containing a main slide valve 3I and an auxiliary slide valve 32 adapted to be operated by the piston26 through the piston stem 33.

'Ihe vent valve device, indicated generally at 22, comprises a piston 34 having the piston chamber 35 on one side thereof connected to the passage 36 leading to the seat of the slide Vvalve 3l. A vent valve 31 contained in the valve chamber 3B is adapted to be operated by the piston 34 through the piston stem 39.

The inshot valve, indicated generally byv the reference character 23, comprises a valvepiston or movable abutment 40 having a stem 4I adapted ber 43. A spring 44 urges the valve piston l46 into engagement with a seat rib 45 and normally holds the valve 42 unseated. The valve 42 has a spring 46 associated therewith and urging the valve 42 into engagement with the seat rib 41 on movement of the p-iston 48 to the left as Viewed inthe drawing.

The inshot valve device 23 has means associated therewith to Ventthe chamber 50 onthe spring side of the piston or movable abutment 40, and as shown in the drawingythis means comprises aY valve element 5I having al grooved stem portion 52 positioned in a passage communicating with the chamberV 59 and having a seat portion 53 adapted to engage a seatV formed in the casing section 54 andY surrounding the passage leading from the chamber 58. A spring 55 is provided which normally' presses thegvalve member 5I to the right as viewed in the drawing so as tocut off communication between the chamber 50 and the atmosphere. v

The timing valve device 24 comprises afflexible diaphragm adapted to engage a'seat rib 9| and subject to the pressure of aV spring 92 which urges the diaphragm away from the'vseat rib. The chamber 93 on one side of the diaphragm 98 is connected to a passage 94 leading to the valve chamber 28 and a chamber 95 onfthe opposite side of the diaphragm is connected to the brake cylinder passage 8. Y Y

In operation, when the brake'pipe 4 is charged with fluid lunder pressure fluid flows through the passage 5 to the piston chamber I5, andthe piston VI5 being rvin the release position as'shown in the drawing, fluid under pressure Vflows from the piston chamber I5 through the feed groove 63 to the valve chamber I1 and thence through the passage I I to' the auxiliary reservoir 9 thus charging the auxiliary reservoir at the pressure carried in the'br'ake pipe. Y v

In the release position of the triple valve, the emergency reservoir passage I4 registers with a port 64 through the main slide valve I 8, which port is now uncovered by the auxiliary valve I9 so that fluidfunder pressure is supplied from the valve chamber II1 to 'charge the emergency reservoir I2 with fluid at lthe pressure carried in the'brake pipe.Ak In the release position the brake cylinder 6 is connected to the atmosphere through the pipe 1,"theY passage 8 past the open inshot valve 42 to the passage 65 and through the cavity 66 in the main slide valve I8 to the atmosphericV exhaust passage 61. Y Y Y lFluid from the brake pipe 4 also flows through the passage 5 tothe piston chamber 21 of the emergency valve device 2l and with the `piston 26 in the release position as 'shown` in' the drawing fluid flows from the piston chamber 21 through the port 68 to the passage 29 and thence to the quick action chamber 36 and to the emergency valve chamber 28.

If it is desired to effect a service application of the brakes, a gradual reduction in brake pipe pressure is made and the triple valve piston I 6 is thereby shifted from the release position, rst moving the graduating valve I9 to uncover the service port (i9 and to close the port 64. The main slide valve I8 is then moved by the piston I5 until the service port 69 registers with the passage 65.

Fluid under pressure is then supplied to the brake cylinder through the passage 65 to the valve chamber 43 of the inshot valve device 23 and thence past the open inshot valve 42 through the passage 8 Vin the brake cylinder. The cham- ;ber. 58 on the spring side of valve piston 48 is connected by a passage 12 leading to the seat ofV the emergency slide valve 3I. In the release position of the valve 3I a cavity 13 connects the passage 12 Vwith the passage 65 so that the chamber 58 is subject to the pressure of fluid flowing to the brake cylinder in effecting a service application of the brakes. A passage 14 connects the chamber 50 with a chamber 15 at the opposite side of the Valve pistonA 48 and outwardly of the seat rib 45 so that during a service application of the brakes the'fluid pressures on the opposite sides of the valvel piston or movable abutment areV maintained equal, permitting the spring 44 to hold the valve piston against the seat Arib 45 and to hold the valve 42 unseated.

Upon a gradual service rate of reduction in the brake pipe pressure the emergency piston 26 is moved so as to shift the auxiliary valve 32 to a positionin which the port 16 in the auxiliary valve32 registers with a port 11 in the main valve 3|, the port 11 registering with an atmospheric exhaust passage 18 so that fluid underv pressure is vented from the valve chamber 28 to the atmosphere. The rate at which fluid pressure in the valve chamber 28 and in the quick action chamber 38 is reduced isequal to the rate at which the brake pipe pressure is reduced in effecting a service application, so that if the rate of reduction in brake pipe pressure does not exceed the service rate the piston 26 will not be operated to shiftthe'main valve 3I to the emergency application position.

When the brake pipe pressure is increased to effect a release of the brakes the triple valve piston I6 is shifted to the release position in which the feed groove 63 is open to permit the recharge of the auxiliary reservoir 9 from the brake pipe and in which the brake cylinder 6 is connected to the atmosphere through cavity 66 as hereinbefore described.

Upon a sudden emergency rate of reduction in brake pip-e pressure the triple valve piston I6 is shifted to application position as in a service 'application of the brakes so that fluid under pressure is supplied from the auxiliary reservoir to the brake cylinder as hereinbefore described.

The emergency piston 26 is also moved to emergency position by a sudden reduction in brake pipe pressure, and the main slide valve 3I is shifted'to a position in which the passage 36 is uncovered by the slide valve 3|; Fluidr under pressure is then supplied from the valve chamber 28 to the quick action chamber 30 through the passage 36 to the piston chamber 35. The quick action piston 34 is then actuated to effect the unseating of the vent valve 31, and thereby fluid emessa isvented from vthe 'brake pipe to the atmosphere by way ci passage Si. past the unseated 'valve 3l to chamber le which is Aopen tothe atmosphere through the port 80. i f

ln emergency position a cavity 874 in the emergency slide' valve 3l connects-the passage il! with the passa/ge lso 'that under pressure is supplied from the emergency reservoir i12 to 'the brakeeyllinde'r passage $5 and thence tothe brake cylinder.

In the release position the chamber 50 on the spring side-of the valvek piston for movable abutment #U is at atmoshperic pressure since' the chamber 50 is connected to the brake cylinder passage t5 through the passage '12, so that when the vemergency slide valve 3l is moved to the emergency position, 'the "passage "12 'being blanked by the Aslide valve 3l, the vcl'ianarer '50 'remains at atmospheric pressure. When the pressure of vfluid 'flowing to the brake cylinder in an emergency application Aof the brakes has been "increased to such a degree -on the 1area `l of the vval-ve piston i0 within the seat rib -4'5 which -is ex-posed to such pressure as to overcomethe "pressure of the spring 4i the valve pis-ton M will be `shifted to `tire left permitting the lvalve 42 "teseat. 'I 'he rapid flow of uid to the brake cylinder'is then out `olf but 'the pressure of iluid supplied 'to the brake 4cylinder during thisV initial inshot issu-ilicient toeliect the movement of the brake cylinderp'iston so as to cause thebrake `shoes to engage the wheels.

With the valve 42 seated fluid *can vilow to 'the brake cylinder only by way vof 'a restricted port `82 and during the period `that' duid is flowing to the brake cylinder by `way of this restricted port the brake cylinder pressure is built up at a suinciently slow rate to permit the slack in the train to run in Witllou't, ycausing excessive shocks.

There is a possibility, however, that leakage of 'ilu'id 'imder lpressure lto v'the chamber Vlill -on Vthe 'spring side of ythe piston 4U will interfere with the intended operation of the piston 4B and the valve means controlled thereby'.

In the vequipment provided by my invention means is provided to vent the chamber yon 'the spring side of the piston cso as tofprevent the building up of pressure 'in this chamber when the piston has been moved to a position to permit the valve associated "therewith l'to restrict the rate of iiow of fluid to the brake cylinder. As will be seen in the drawing when the piston 4U is moved "to the left against the pressure of the spring 44 as a result of the building up of fluid under pressure on the opposite face'of the vpiston it engages .the end of the stem 52 of the valve element 5l so as to move the valve element away from the, seat formed in the casing section `54 and permits any fluid under pressure in the 'chamber to escape to the'atmosphere'through the 'passage lili.Y 'Ilhe valve 5l is held-open lso that there can be no building up of pressure inthe chamber 5l) as Ia result of leakage of fluid under pressure into the chamber andthe valve 2, therefore, will remain seated.

In an `emergency application .fluid under pres'- sure supplied from the valve chamber 28 to the quick action chamber 35 Vis gradually vented vto the atmosphere by way of port 86 through the emergency piston 34 so that the pressure .in the valve chamber 28 and vquick action chamber 3S n is gradually reduced. l i

The quick action chamber pressure -actsrfin the chamber A93 pn the diaphragm 90 of the timing Valverde-ideen and the pressure of the supplied -to :the brake cylinder acts on the lopposite sid-e ofthe diaphragm in chamber B5. As a consequence after a period of 'time 'when the increase in brake cylinder pressure in the chamber $5 plus the pressure fof the spring 92 is sullicient to overcome the reducing :qu-ick action chamber pressure in the chamber 93 the diaphragm mi will be shifted 'to the lright soas to open communic'ati-on from the chamber 95 past the seat rib 9| to the passage 6,5.

The fluid pressure supply passage -is thus directly Vconnected 'to the brake cylinder passage 8 permitting the brake ycylinder 'pressure to be built up at a rapid rate.

From the foregoing it will be seen that the brake equipment provided by my invention has means operable subject tothe pressure of iluid supplied to the brake cylinder during an emergency operation of the equipment to control the rate fol .'ow lof fluid to the brake cylinder and that it .has means to insure that the operation of .this means will not be aliected by leakage of fluid .around the valve means or the elem-ents associated therewith or to other portions of the brake controlling equipment.

kWhile one embodiment of the invention has been illustrated and described in detail it should be understood that the invention is not limited to these details'and that numerous modifications and changes may be made without `departingirom the fscope of the following claims.

I Having now described my invention, what I claim as new and desire to secure by Letters Patent, is: asl' 1. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve device controlling the supply and Vrelease of fluid under pressure to and from the brake cylinder, the valve device having a service position and an emergency position, and valve means having a valve element controlling the rate .at which iluid under 'pressure is vsupplied to the brake cylinder, said valve means having a movableabutment subject on one side to the pressure of fluid supplied to the brake cylinder and subject on the other side tothe pressure of fluid 'in a chamber communicating with the passage through `Wlfiic-hfluid under pressure is supplied the brake cylinder, means operable on movementfo'f the brake controlling valve device to the 'emergency position to cut oi the communication through which iiuid under pressure is supplied to sai-d chamber, a communication between said chamber and the atmosphere, and means controll-ing xthe flow of uid through said communication.`

2v. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a 'brake controlling valve device controlling the supply and release -of fluid under pressure to and from the brake cylinder, the valve device having a service posi- 'tion `and an emergency position, and valve means having a valve element controlling lthe rate of which Viiuid `under pressure is supplied to the 6% 'brake cylinder, said valve means having a movable abutment subject on one side to the pressure of fluid .supplied to the brake cylinder and subject on the other side to the pressure of u'id in 7.0

,a chamber communicating with the passage through which *fluidV under pressure is supplied to the brake cylinder, biasing means associated with said valve means and normally urgingthe abutment to aV position in which the valve element associated therewith is in a position to permit uid to ow to the brake cylinder at one rate, means operable on movement of the brake controllingA valve device to the emergency position to cut off the communication through which fluid under pressure is supplied to said chamber, a communication between said chamber and the atmosphere, and meanscontrolling the ow of fluid through said communication. Y

3; In a uid pressure brake, in combination, a brake pipe, a brake cylinder, abrake controlling valve device controlling the supply'and release of iluid under pressure to and from the brake cylinder, the brake valve device having a service position and an emergency position, and valve means having a valve element controlling the rate at which the uid under pressure is supplied to the brake cylinder, said valve means havinga movable abutment subject on one side to the pressure of fluid supplied to the brake cylinder and subject on the other side to the pressure of fluid in a chamber communicating With the passage through which iiuid under pressure is supplied tothe brake cylinder, means-operable on movement of the brake controlling valve device to the emergency position tocut 01T the com- Vimmication through which uidunder pressure is supplied to said chamber whereby pressures of different values are operative on'opposite sides of the abutment and whereby the abutmenlt is moved to a position to permit the valve element associated therewith to move to a position to restrict the flow of fluid to the brake cylinder, a-.passage communicating with said chamber and with the atmosphere and valve means associated with the movable abutment and controlling said passage, said valve means being adapted to open said passage when the movable abutment is moved to a position to permit the valve element associated therewith to move to a position torestrict the flow of fluidto the brake cylinder.

Q4. Ina fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve device controlling the supply and release of fluid under pressure to and from the brake cylinder, the brake controlling valve device havingVV a serviceportion and an emergency portion, and valvev means having aV valve element controlling the rate at which fluid under pressure is supplied to the brake cylinder, said valve means having a movable abutment subject on one side to the pressure of fluid supplied to the brake cylinder and subject on the other side to the pressure of the fluid in a chamber communicating with the passage through which uid under pressure is vsupplied to the brake cylinder, biasing means associated with said valve means and normally urging the abutment to a position in which the valveelement associated therewith is in a position to permit fluid to flow to the-brake cylinder at one rate, means operable on movement of 'the brake controlling valve devicev to the emergency position to 4out off communication through which fluid under pressure isrsupplied to said chamber whereby fluid pressures of different, values are operative on differentfside's of the abutment and whereby the abutment is lmoved against thebiasing means to a position to permit the valve element associated therewith ltomoveto a position to r'estrict'the flow of iluid to the' brake cylinder, a passage communicating with said chamber and with the atmosphere, and valve means Y'associated vwith the movable abutment and controlling V.said passage, said valve means'being adapted to open said passage when the movable abutmentis moved to .a position to permit the valve element associated therewith to moveto ar position to-restrict the flow of fluid to the brake cylinder.

v5. ,Inria uid pressurebrakavin combination,

a brake pipe, a brake cylinder; an auxiliary reservoir, an emergencyreservoir, a brake controlling -valvedevice havinga service portion operated lon a reduction in brake pipe pressure to supply iluid under pressure from the auxiliary reservoir tov the Vbrake vcylinder` Aand an emergency portion operated on asudden reduction in brakepipe pressure to supply iiuid under pressure to the Vbrake cylinder from the emergency reservoir, and a valve device having a'valve element controlling the rate at which fluid issupplied to the-brake: cylinder, theivalveI device comprisingga movable` abutment subject on one side to the pressure of ,thefluid supplied to the brake "cylinder, andrsubject on the other side to the pressureA of the fluid in a chamber communicating with the pass-age through which iiuid under pressure is supplied tothe brakecylinder, biasing means associated with said valve device and urgingthe valve :element to aposition to permit fluid under pressure to iiow. to the brake cylinder Vat'one rat,e, the emergency portion of the brake controllingv-alve device having means associated therewith land operablevto cutoff-the flow of fluid to saidochamber .when said emergency portion of the valve device is in a position to permit fluid to flow from the emergency reservoir to the brakecylinder, a-passage communicating with said ch-amber and Withthe atmos- `phere, and valve means controlled by saidmovable abutment andl controlling .the communication through said-passage, Ysaid valve means being adapted to open said passage when the abutment. is moved to. a position topermit the valve element .associated therewith and controlling the rate Vof flow offluid to the brake cylinder to move toa positionto restrict ,the flow of uid to the .brake` cylinder.`

6. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve -device controlling thesupply and release of fluid under pressure to and from the brake cylinder and comprising a service portion operated ona reductioniin brake pipe pressure to supply fluid under pressure to the brake cyl- 'inder and an-emergencyportionoperated on a sudden reduction in. brake pipe pressure to sup- -ply uid under pressure to the brake` cylinder, and valve means having afvalve `element controlling the rate at whichuid is supplied to the brake-cylinder, the valve means including a movable abutment associated with said valverelement and subjecton onesideto jthe pressure of the fluid supplied to v the,brakecylindery and subject on the other side ,tov the pressure of fluid in a chamberV communicating` with the passage Ythrough which fluid is supplied to the brake cylinder, and. meanscontrolled by theemergency portionof ythe brake Vcontrolling valve device to cut off the communication through which said chamber is supplied Awith uid under pressure when said emergencyVV portion is conditioned to supply fluid to the brake cylinder, a passage communicating withsaid chamber and vwith the atmosphere, and valve means controlled by said vmovable abutment and controlling communication through said passage, said valve means being adapted to open said passage when the movable abutment is moved to a position to permit the valve element associated'therewith and controlling the rate of flow of fluid to the brake cylinder to move to a position to restrict the ilow of uid to the brake cylinder.

7. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve device controlling the supply and release of fluid under pressure to and from the brake cylinder and comprising a service portion operated on a reduction in brake pipe pressure to supply iiuid under pressure to the brake cylinder and an emergency portion operated o-n a sudden reduction in brake pipe pressure to supply fluid under pressure to the brake cylinder, and valve means having a valve element. controlling the rate at which fluid is supplied to the brake cylinder, the valve means including a movable abutment associated with said valve element and subject on one side to the pressure of the fluid supplied to the brake cylinder, and subject -on the ther side to the pressure of fluid in a chamber communicating with the passage through which iluid is supplied to the brake cylinder, biasing means associated with said abutment and urging the valve element to a position to permit fluid under pressure to flow to the brake cylinder at one rate, and means controlled by the emergency portion of the brake controlling valve device to cut olf the communication through which said chamberis supplied with fluid under pressure when said emergency portion is conditioned to supply uid to the brake cylinder, a passage communicating with said chamber and with the atmosphere, and valve means controlled by said movable abutment and controlling communication through said passage, said valve means being adapted to open said passage when the movable abutment is moved to a position to permit the valve element associated therewith and controlling the rate of flow of fluid to the brake cylinder to move to a position to restrict the flow of fluid to the brake cylinder.

8. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve device operated upon a reduction in brake pipe pressure for supplying fluid under pressure to the brake cylinder, valve means for controlling a communication through which fluid under pressure is supplied to the brake lcylinder, a movable abutment subject on one side to the pressure of fluid supplied to the brake cylinder for operating said valve means to effect a reduction in the rate of flow of fluid to the brake cylinder and means operated by said abutment for venting the chamber at the opposite side of the abutment.

9. In a fluid pressure brake, in combination, a brake controlling valve device operated on a`n emergency reduction in brake pipe pressure for supplying fluid under pressure to the brake cylinder, valve means for controlling a communication through which said brake controlling valve device supplies fluid under pressure to the brake cylinder, a movable abutment normally maintaining said valve means in the open position and movable upon a predetermined increase in brake cylinder pressure acting on one side to permit said valve means to close, and a Valve operated by the movement of said abutment for venting the chamber at the opposite side of said abutment.

, 10. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve device controlling the supply and release of iluid under pressure to and from the brake cylinder, the valve device having a service position and an emergency position, valve means for controlling a communication through which uid under pressure is supplied to the brake cylinder, a movable abutment for operating said valve means, said movable abutment being subject on each side to the pressure of fluid supplied to the brake cylinder on movement of the valve device to the service position, and means operable on movement of the valve device to the emergency position for cutting off the communication through which fluid is supplied to one side of said abutment and for opening a communication through which the chamber on said side of the abutment is vented.

11. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve device controlling the supply and release of fluid under pressure to and from the brake cylinder, the valve device having a service position and an emergency position, valve means for controlling a communication through which lluid under pressure is supplied to the brake cylinder, a movable abutment for operating said valve means, said movable abutment being subject on each side to the pressure of iluid supplied to the brake cylinder on movement of the Valve device to the service position, means operable on movement of the valve device to the emergency position for cutting off the communication through which fluid is supplied to one side of thel abutment, and means operated by said abutment for venting the chamber on said side of the abutmen 12. In a fluid pressure brake, in combination, a brake pipe, a brake cylinder, a brake controlling valve device controlling the supply and release of fluid under pressure to and from the brake cylinder, the valve device having a service portion and an emergency portion, valve means controlling a communication through which uid under pressure is supplied to the brake cylinder, a movable abutment for operating said valve means, said abutment being subject on one side to the pressure of fluid supplied to the brake cylinder, and being subject on the other side to the pressure of iluid in a chamber communicating with the communication through which fluid under pressure is supplied to the brake cylinder, means controlled by the emergency portion of the valve device and operable on movement of the emergency portion of the valve device to a position to supply fluid to the brake cylinder to cut 01T the communication through which fluid is supplied to said chamber, and means operated by said abutment for venting said chamber.

JOHN N. GOOD. 

